The invention relates to a hand gun designed in particular for crop spraying, that is, a hand-held device used in spraying or dusting crops, say with leaf fungicides or fertilizers, or at all events in spreading or projecting a given liquid for whatever purpose, including washing and hosing, at pressures of 10 to 50 bar and more.
The prior art embraces a conventional lance-type implement that is operated with two hands, one hand closing around the grip, the fingers of which work the on-off valve, and the other operating the lever of a jet control valve that is situated beneath the barrel and designed to swing through a longitudinal vertical plane.
Another prior art gun, operated with one hand only, is designed such that the index and other fingers close on the lever of the on-off valve, whilst the jet control valve lever, mounted forward of the on-off valve and to one side, is operated with the tip of the thumb.
A further gun that can also be operated with one hand is provided with a single lever, located in the body of the handgrip and manoeuvred with the fingers, that shifts within a longitudinal vertical plane through a first angular position, producing operation of the on-off valve, and into a further sector that controls the jets; the other hand can be employed to position and tighten a pair of nuts on a longitudinally disposed threaded rod, so as to select and hold a given type of jet.
The gun first mentioned requires the use of both hands at all times, and thus keeps the operator fully occupied; the gun with the side-mounted lever cannot realistically be considered practical, at least when in use for any length of time, in view of the difficulty experienced in thumb-operation that derives from the considerable resistance set up by pressure of the controlled liquid; despite the advantage of its single-lever embodiment, the third gun mentioned still requires the use of the other hand to lock the lever in position, and the locking mechanism must be released to permit applying the on-off valve, which signifies loss of time, and again, the use of both hands, with all the attendant drawbacks.
Thus, the prior art stands in need of considerable improvement with regard to elimination of the aforementioned drawbacks, which in most instances are attributable to the fact that the control lever of a rotary control valve has to be swung between two limit positions -viz, a first position designed to produce a freely-discharging long jet of liquid, and a second designed to render the discharge as vortiginous as possible for producing a fine atomized spray; also, the provision of an an automatic locking facility on the main jet-adjustment settings would be desirable.